Redhat Study notes:
To identify the architecture of a system, run the following command:
# uname -p
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If you’re planning to configure VMs on RHEL 6, be sure to choose an architecture
that supports hardware-assisted virtualization, along with Basic Input/Output System
(BIOS) or Universal Extensible Firmware Interface (UEFI) menu options that
allow you to activate hardware-assisted virtualization. A configuration that supports
hardware-assisted virtualization will have either the vmx (Intel) or svm (AMD) flags
in the /proc/cpuinfo file.
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Red Hat officially requires 512MB of RAM and recommends at
least 1GB of RAM per system
Of course, actual memory requirements depend on the load from every program
that may be run simultaneously on a system. That can also include the memory
requirements of any VMs that you might run on a physical RHEL 6 system. There
is no practical maximum RAM, as theoretically, you could run 128TB (that’s
128,000GB) of RAM on RHEL 6. But that’s just theory. The maximum RAM
supported by Red Hat on RHEL 6 is 16GB on 32-bit systems and 2TB on 64-bit
systems.
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If you’re setting up Linux as a server, RAM requirements increase with the
number of users who may need to log in simultaneously. The same may be
true if you’re running several different VMs on a single system. However,
administrators typically “overbook” RAM on VMs configured with different
functionality.
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Bare-metal virtualization :
Some VM systems include a minimal operating system dedicated to VM operation.
Two examples of bare-metal virtualization systems are VMware ESX and Citrix XenServer.
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The KVM solution configured with RHEL 6 is known as a hypervisor, a VM
monitor that supports the running of multiple operating systems concurrently on the
same CPU. KVM replaces the previous default, Xen.
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Different subscriptions are available for the desktop and the server. While the
RHCSA is focused on workstations, it also does require the configuration of HTTP
and FTP servers. Of course, the RHCE also requires the configuration of a variety of
server services. So most readers will need a server subscription.
A variety of server subscriptions are available, depending on the number of CPU
sockets and virtual guests. A system associated with a regular RHEL subscription is
limited to two CPU sockets and one virtual guest. Each socket can have a multicore
CPU. Significant discounts for academic users are available.
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Under trademark law, Red Hat can prevent others from releasing software with its
trademarks, such as its red fedora symbol. Nevertheless, the GPL gives anyone the
right to compile that source code. If they make changes, all they need to do is release
their changes under the same license. And several “third parties” have taken this
opportunity to remove the trademarks from the released source code, and compiled
that software into their own rebuilds, functionally equivalent to RHEL.
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RHEL Distributions:
1- Community Enterprise Operating System (CentOS)
The rebuild known
as CentOS includes a number of experienced developers who have been
working with RHEL source code since the release of RHEL 3 back in 2002.
For more information, see www.centos.org.
2- Scientific Linux
This distribution is developed and supported by experts
from the U.S. Government’s Fermilab and the European Organization
for Nuclear Research, known by its French acronym, CERN. The people
associated with these labs are among the smartest scientists around. For more
information, see www.scientificlinux.org.
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Since Linux filesystems are efficient, they can be filled to near capacity with
minimal defragmentation issues. If you’re configuring VMs on Microsoftformatted
partitions, considerable additional free space is required due to
volume fragmentation.
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Before installing RHEL 6, it may be helpful to review what is known about the latest
RHCSA and RHCE exams. As described in the Red Hat blog announcement at
http://redhatcertification.wordpress.com/, Red Hat now provides:
■ Pre-installed systems
■ Questions presented “electronically”
In other words, when seated for an exam, you’ll see an installed copy of RHEL 6
on the test system, with questions in some electronic format. No public information
is available on the format of the questions. This book will assume the most basic
format for Red Hat exam questions, text files available in the root administrative
user’s home directory, /root.
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The Advantages of Network Installation
Network installation means you don’t have to use a full DVD on every system when
installing RHEL 6. It means that every system is installed from the same set of
installation packages. Network installations are faster than those from physical DVDs.
Network installations become especially powerful when combined with Kickstart
files and the Pre-boot eXecution Environment (PXE). In that configuration, all
you need to do to install RHEL 6 is boot a system, point the remote installer to the
appropriate Kickstart file, and voila! After a few minutes, you’ll have a complete
RHEL 6 system.
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The baseline minimum installation of RHEL 6 does not include a GUI. While it
is fairly easy to install the package groups associated with the GUI after installation
is complete, that process requires the installation of several hundred MB of packages.
And that takes time.
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Since Red Hat provides a pre-installed system for the exam to reduce the time required for the exam, it is reasonable to suggest that the system provided by Red Hat includes the GUI. And the default GUI for Red Hat systems is the GNOME Desktop Environment.
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